I am working in a Web Project in Visual Studio 2008. When I hit F12 (or right-click and select Go To Definition) Visual Studio is consistently going to the Metadata file in
It happens when you don't add reference as a project but point to a dll or exe using Browse tab in Add Reference dialog. If you add reference using Projects tab you should go directly to the source code when you select Go To Definition.
However, if you install ReSharper, you'll go to source code even if you added your reference to a dll/exe using Browse tab.